Alien Comet Cloud Spotted Around Faraway Star

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Comets detected around other stars appear strikingly similar to
the most primitive comets in the solar system, researchers say.

The discovery suggests that matter around distant stars mixed in
ways similar to
the solar system in its youth, scientists added.

Astronomers have detected thousands of alien
planets orbiting distant stars. In addition to these
exoplanets, scientists have begun discovering vast clouds of
extrasolar comets, including balls of ice and rock that may be
pelting these far-off worlds. Researchers think massive numbers
of comets bombarded Earth billions of years ago, delivering not
only the water that now makesup the oceans,but potentially the
organic ingredients of life.

Alien comets

To learn more about alien comets, astronomers focused on the
Beta Pictoris system, about 63 light-years from Earth.

Beta Pictoris is a young (12 million years old) analog of the
solar system: Its star has a disk of debris around it full of
small grains of dust, and at least one planet relatively close
it, about 10 times the distance from the Earth to the sun (10
astronomical units, or roughly 930 million miles – 1.5
billion kilometers).

The scientists used the European Space Agency's
Herschel Space Observatory to scan Beta Pictoris. Materials
around a star absorb some of its light, resulting in patterns
known as spectra that allow scientists to identify what the
materials are.

The researchers looked for signs of olivine crystals around Beta
Pictoris. This olive-green crystal is typically magnesium-rich
when it first forms in space, as is seen in the most ancient
comets in the solar system, unlike the more iron-rich olivine
seen in asteroids.

Comet cloud of Beta Pictoris

In the cold outskirts of Beta Pictoris, about 15 to 45
astronomical units from the star, the Herschel spectra revealed
that the olivine is rich in magnesium. In addition, these
crystals comprise about 3.6 percent of the dust around Beta
Pictoris, making the dust strikingly similar in composition to
the most primitive comets in the solar system, such as 17P/Holmes
and 73P/Schwassmann–Wachmann, which are about 2 percent to 10
percent crystalline olivine.

"I find it stunning that we were able to detect the spectral
fingerprint of this material in another planetary system," said
lead study author Bernard Lammert de Vries, an astrophysicist at
KU Leuven University in Belgium. "The dusty disks in these
systems are very faint."

Olivine crystals in space can form only within 10 astronomical
units of stars. The fact that comets are typically seen much
farther out suggests this material is regularly slung away from
stars. The similar levels of crystalline olivine seen in Beta
Pictoris' dust and the solar system's ancient comets suggest that
matter around these stars may have mixed in similar ways, even
though Beta Pictoris is 1.5 times more massive than the sun and
eight times brighter.

"This is a step towards a better understanding of planet and star
formation," de Vries told SPACE.com.

The scientists detail their findings in the Oct. 5 issue of the
journal Nature.